1. Field of the Invention
The present invention relates to an image-capturing device that utilizes a solid image-capturing element and an electronic camera provided with the image-capturing device.
2. Description of the Related Art
Image-capturing devices in the known art include those that employ two-dimensionally arrayed photoelectric conversion elements such as photodiodes to convert light to electrical charges corresponding to the light intensity distribution, transfer the stored charges from the individual photoelectric conversion elements to a floating diffusion amplifier via a charge transfer element such as a CCD (charge-coupled device) and generate an output achieved by converting the stored charges to voltages and amplifying them.
FIG. 5 illustrates the structure of an image-capturing device in the prior art.
A plurality of photoelectric conversion elements 1 are two-dimensionally arrayed on a semiconductor substrate (silicon substrate) 20. A charge transfer element 2 is provided in correspondence to each column of photoelectric transfer elements 1 to transfer the stored charges in the direction of the column. A charge transfer element 3 that transfers electrical charges in the direction of the row is connected at the ends of the individual column charge transfer elements 2 along the direction of their charge transfer so that the charges that have been transferred in the direction of the column are further transferred in the direction of the rows. A floating diffusion amplifier 4 is connected to the end of the row charge transfer element 3 along the direction of its charge transfer to output voltages achieved by converting the electrical charges to voltages and then amplifying them through an output terminal 8.
In this specification, the floating diffusion amplifier, which is connected at the end of charge transfer elements along the direction of transfer and converts the transferred charges to voltages and then amplifies them, is to be simply referred to as an “output amplifier.”
The output amplifier 4 is connected to a positive source 7 and is also connected to a negative source 6 via a resistor 5, with a bias current corresponding to a source voltage applied between the positive source 7 and the negative source 6 flowing through the output amplifier 4. The resistor 5 is a resistor provided for bias current adjustment. It is to be noted that while power is supplied to the photoelectric conversion elements 1 and the charge transfer elements 2 and 3, the illustration of their power circuits is omitted.
However, in the image-capturing device in the prior art described above, in which the photoelectric conversion elements 1, the charge transfer elements 2 and 3 and the output amplifier 4 are provided on a single semiconductor substrate 20, the heat generated at the output amplifier 4, which generates a great deal of heat, is communicated to the photoelectric conversion elements 1 in the vicinity over time, as illustrated in FIG. 6. As a result, the photoelectric conversion elements 1 located closer to the heat source, i.e., the output amplifier 4, become heated to generate a large dark current, which, in turn, raises the black level of the image signal, as shown in FIG. 7, to cause a so-called “dark current shading” in the vicinity of the heat source.